[r=axwalk],[bug=1301467] testing: reattempt MgoInstance.run if addr in use
[r=axwalk],[bug=1301467] testing: reattempt MgoInstance.run if addr in use

Mongod does not support listening on port 0 to
acquire an ephemeral port, so our tests must
choose a port which may then be allocated to
another process. This CL adds code to reattempt
the starting of mongod if the port is in use,
up to a maximum of 5 attempts.

https://codereview.appspot.com/94410046/
tasdomas/juju,marcmolla/juju,alesstimec/juju,makyo/juju,waigani/juju,reedobrien/juju,AdamIsrael/juju,mjs/juju,dimitern/juju,perrito666/juju,rogpeppe/juju,dooferlad/juju,voidspace/juju,AdamIsrael/juju,axw/juju,mjs/juju,howbazaar/juju,mikemccracken/juju,bogdanteleaga/juju,gabriel-samfira/juju,davecheney/juju,anastasiamac/juju,anastasiamac/juju,dooferlad/juju,voidspace/juju,macgreagoir/juju,rogpeppe/juju,marcmolla/juju,bogdanteleaga/juju,makyo/juju,bz2/juju,reedobrien/juju,frankban/juju,frankban/juju-tmp,jrwren/juju,marcmolla/juju,tsakas/juju,mattyw/juju,perrito666/juju,macgreagoir/juju,thomnico/juju,kat-co/juju,dimitern/juju,frankban/juju,AdamIsrael/juju,thomnico/juju,marcoceppi/juju,marcoceppi/juju,howbazaar/juju,dooferlad/juju,bac/juju,mjs/juju,mikemccracken/juju,howbazaar/juju,Altoros/juju-vmware,howbazaar/juju,ericsnowcurrently/juju,anastasiamac/juju,axw/juju,dimitern/juju,fwereade/juju,frankban/juju,cmars/juju,bac/juju,cmars/juju,mjs/juju,Altoros/juju-cloudsigma,sinzui/juju,cherylj/juju,mikemccracken/juju,wwitzel3/juju,bz2/juju,mhilton/juju-juju,bac/juju,waigani/juju,cloud-green/juju,bz2/juju,Altoros/juju-vmware,axw/juju,bz2/juju,makyo/juju,frankban/juju,davecheney/juju,fwereade/juju,cloud-green/juju,reedobrien/juju,bac/juju,frobware/juju,anastasiamac/juju,Altoros/juju-cloudsigma,waigani/juju,fwereade/juju,gabriel-samfira/juju,ericsnowcurrently/juju,frobware/juju,cmars/juju,kat-co/juju,frankban/juju-tmp,bogdanteleaga/juju,cherylj/juju,mhilton/juju-juju,perrito666/juju,bogdanteleaga/juju,alesstimec/juju,gabriel-samfira/juju,cherylj/juju,Altoros/juju-vmware,fwereade/juju,tasdomas/juju,sinzui/juju,tych0/juju,ericsnowcurrently/juju,wwitzel3/juju,cloud-green/juju,alesstimec/juju,frobware/juju,mjs/juju,dooferlad/juju,alesstimec/juju,dooferlad/juju,kat-co/juju,sinzui/juju,bac/juju,perrito666/juju,mhilton/juju-juju,mhilton/juju,waigani/juju,wwitzel3/juju,makyo/juju,dimitern/juju,mhilton/juju-juju,thomnico/juju,howbazaar/juju,mattyw/juju,voidspace/juju,jrwren/juju,tsakas/juju,macgreagoir/juju,reedobrien/juju,thomnico/juju,marcoceppi/juju,axw/juju,cherylj/juju,reedobrien/juju,gabriel-samfira/juju,Altoros/juju-cloudsigma,mjs/juju,mhilton/juju,tasdomas/juju,perrito666/juju,tasdomas/juju,dimitern/juju,tych0/juju,davecheney/juju,frankban/juju-tmp,marcoceppi/juju,tych0/juju,mhilton/juju,frankban/juju,frankban/juju-tmp,jrwren/juju,tsakas/juju,AdamIsrael/juju,davecheney/juju,mjs/juju,tsakas/juju,alesstimec/juju,cloud-green/juju,mattyw/juju,marcmolla/juju,ericsnowcurrently/juju,cmars/juju,sinzui/juju,kat-co/juju,anastasiamac/juju,kat-co/juju,voidspace/juju,Altoros/juju-vmware,wwitzel3/juju,mhilton/juju,marcmolla/juju,mattyw/juju,axw/juju,mikemccracken/juju,rogpeppe/juju,Altoros/juju-cloudsigma,ericsnowcurrently/juju,bz2/juju,mikemccracken/juju,macgreagoir/juju,gabriel-samfira/juju,tych0/juju,macgreagoir/juju